Long Island Power Authority rates are rising by about 4 percent in September.
The power authority pinned the second summer increase on higher energy costs and peak-season usage.
"The power supply charge is the monthly pass through to customers for what we pay for energy," said Mark Gross, a LIPA spokesman. "We make no profit on this. Every utility has a power supply charge that they pass through to customers. It goes up and down pending on market conditions."
Gross also said the increase could be short lived, as the average temperature drops. He said July had four of the 12 top usage days in LIPA's history, which dates back to the late 1990s.
Gross added that LIPA's power supply charge has dropped in five of the last eight months.